The following discussion of machines is included in this specification solely for the purpose of providing a context for the present disclosure. It is not suggested that any of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present disclosure.
An auger boring machine is a type of boring machine that uses a rotatable cutting head to cut the earth, and a driven auger to transport the spoil away from the cutting head. A casing is used to retain the integrity of the bore and to allow the spoil to be transported along the bore. The casing may also be left in place after the bore is complete to provide a conduit for services to pass there through. An auger boring machine is often used where services need to be laid underground and it is not convenient to dig a trench, such as when passing under a roadway or rail line.
The casing and auger have a tolerance that allows the auger to rotate within the casing, provided the auger and casing are substantially aligned with the selected direction. The casing can be diverted from its selected direction by variations in friction of the outside wall of the casing and the surrounding earth. Alternatively the casing can be diverted by tree roots or floaters.
Failure to maintain the auger and casing substantially aligned with the selected direction can result in the auger rubbing on the inside wall of the casing. This creates friction between the auger and the casing and causes the drive motor to work harder. Excessive misalignment can result in damage or failure of the boring machine.
The inventor is aware of an auger boring machine that has a short casing piece at the front of the main casing, which can pivot relative to the main casing to provide the machine with steering capabilities. A ram is provided external to the main casing which is operable to pivot the short casing piece. This arrangement only allows for steering in one plane. Furthermore, the ram being external to the casing adversely imparts on movement of the casing through the bore and, is susceptible to damage as the casing is moved along the bore.
Obstructions such as a tree root or more critically a floater often block the selected path of the bore. Where this occurs the obstruction needs to be ground up so that it can pass through the cutting head, or between the cutting head and the casing, into the flight of the auger. This is time consuming and can result in dulling of the cutting head.
It would therefore be desirable to provide an auger boring machine that addressed at least one of these problems. It is preferred that the machine be capable of providing a useful alternative to overcoming obstructions in the path of the selected direction. It is also preferred that the machine be configured to substantially maintain alignment with the selected direction.